The following is a description of the background of endotracheal tubes (ETTs). It should be understood that the device and method of the present invention is not limited to the clearing of ETTs but is applicable to a range of artificial tubes such as indwelling catheters, pigtail catheters, abscess drains, and chest tubes and that ETTs are being discussed simply by way of example. It should also be understood that the device and method of the present invention is not limited to secretions but is applicable to a range of accumulating and/or occluding materials such as blood, clots, and ingrown tissues/membranes.
Automated mechanical ventilation is often required for patients under anesthesia and for longer-term breathing assistance in compromised patients. Endotracheal tubes are placed in the upper respiratory tract of patients to provide direct airway access when connected to a mechanical ventilator. Annually, 50 million ETTs are sold globally. Patients intubated with ETTs are unable to effectively clear lung secretions, and therefore secretions can accumulate and partially occlude the inside of the ETT. This leads to increased airway resistance and a potentially negative impact on patient health if not remedied. Without proper air humidification, the secretions also potentially become dried, thick, and difficult to remove.
The most routine method to maintain ETT patency is periodic aspiration with a suction catheter. The suction catheter is designed to be momentarily inserted down the ETT manually while attached to a negative pressure source. There are two general types of suction catheters: open and closed. An open suction catheter requires the patient to be disconnected from the ventilator for the suctioning procedure. A closed suction catheter is enclosed in a protective sleeve and remains attached to the ventilator circuit the entire time. Suctioning can occur without having to shut off the ventilator or disconnect the patient, because there is a diaphragm that maintains an air-tight seal around the suctioning catheter. Whether open or closed, the general suction procedure remains the same. With one hand stabilizing the proximal end of the ETT, the suction catheter is fed into the ETT with the opposite hand until the end is reached, being careful to not over-insert the catheter beyond the tip of the ETT. While retracting the suction catheter, a valve is pressed enabling the negative pressure source to apply a vacuum to the inner lumen of the suction catheter to aspirate out secretions accumulated on the inner wall of the ETT. It is generally desired for the entire suction procedure to be performed in 10-15 seconds, or 5 seconds in children to minimize the impact of the suctioning procedure on lung mechanics and respiration. Generally, a patient will require suctioning every 4-6 hours, but the process may be performed with greater regularity if necessary. The procedure is recommended on an as needed basis, not a regular interval, due to the detrimental effect on the patient.
Attempts to clear the ETT using standard techniques are often ineffective, time consuming, expensive, and an agonizing experience for the patients, families, and health care providers. Standard methods can also dislodge bacteria containing particles into the lungs. Ventilator Acquired Pneumonia (VAP) is a major source of infection in hospitals, and is often due to the direct path to the lungs for bacteria from ETT intubation. Standard suctioning has an effect on lung mechanics, including decreased tidal volume and lung compliance. Clinical side effects include hypoxia (low oxygen in blood), bradycardia (low heart rate), or atelectasis (collapse of part of the lung). In general, the long term effects of acute changes in lung mechanics or cumulative exposures to short term clinical side effects of suctioning on long term respiratory health is not known. Still, minimizing the potential negative impacts of the suctioning process on the lungs is desirable.
Negative effects can be minimized with use of smaller diameter suction catheters, which allow improved airflow during the insertion of the catheter and when actively suctioning. Guidelines suggest choosing a suction catheter whose outer diameter is less than half the inner diameter of the ETT. However, with narrow ETTs (such as neo-natal or pediatric patients) this is difficult to achieve without severely limiting secretion aspiration effectiveness using standard methods. Such small diameter suction catheters may easily clog, depending on the consistency of the secretions. In addition to airflow considerations, larger suction catheters may be difficult to insert if the catheter diameter to ETT inner diameter ratio is larger than 0.7.
While the practice is now largely discouraged, occasionally physiologic saline may be first instilled at the inlet to the ETT in an attempt to hydrate and thin the secretions to encourage its removal during the subsequent suctioning procedure. Additional goals of saline instillation may include lubricating and easing the insertion of the catheter itself, and/or elicitation of a cough from the patient to aid secretion removal. The current methods of instilling saline into ETTs are not precise and there is risk of excess fluid entering the lungs and possibly causing dispersion of adherent contaminating material. Reports further suggest saline instillation may cause greater blood oxygen desaturation than suctioning without saline. Despite lack of evidence supporting saline instillation and its potential risks, some clinicians continue the practice.
When suctioning is unable to restore patency quickly, the only recourse is to replace the ETT, further raising the risk of VAP while also depriving the patient of oxygen until the patient is re-intubated and reconnected to the ventilator. In addition, the re-intubation process itself can agitate the patient's airway and lead to inflammation and/or injury.
There remains a need to safely and quickly clear ETTs, while reducing the negative impact the suction procedure has on the lung mechanics of an already compromised patient.